Correlation of surface phases with electrical behavior in thin-film CdTe devices

Glancing incidence X-ray diffraction (GIXRD) analysis of crystalline surface phases in cadmium telluride solar cells is correlated with device behavior for different processing conditions. GIXRD sampling depths are calculated for different phases and X-ray sources. Air heat treatment of CdTe films forms the native oxide CdTeO , while treatment in CdCl yair vapor forms 32 CdTeO and CdO. Air treatment followed by CdCl yair treatment forms surface oxides, reduces CdS diffusion into CdTe and 32 improves junction performance. The CdTeO surface oxide limits CdCl concentration in the CdTe film, yet allows sufficient 32 CdCl species for CdTeyCdS junction activation. In devices, residual oxide phases contribute to series resistance and current– 2 voltage retrace hysteresis. These effects are mitigated by oxide removal and formation of a Te layer. Addition of Cu to the contact followed by thermal treatment increases open circuit voltage. Optimal cell performance is obtained for Cu y(CuqTe) atomic ratios0.7. 2003 Elsevier Science B.V. All rights reserved.